US20050120644A1 - Precast post-tensioned segmental pole system - Google Patents
Precast post-tensioned segmental pole system Download PDFInfo
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- US20050120644A1 US20050120644A1 US11/011,275 US1127504A US2005120644A1 US 20050120644 A1 US20050120644 A1 US 20050120644A1 US 1127504 A US1127504 A US 1127504A US 2005120644 A1 US2005120644 A1 US 2005120644A1
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Images
Classifications
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/30—Columns; Pillars; Struts
- E04C3/34—Columns; Pillars; Struts of concrete other stone-like material, with or without permanent form elements, with or without internal or external reinforcement, e.g. metal coverings
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/20—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members
- E04C3/22—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members built-up by elements jointed in line
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/20—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members
- E04C3/26—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of concrete or other stone-like material, e.g. with reinforcements or tensioning members prestressed
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
- E04H12/00—Towers; Masts or poles; Chimney stacks; Water-towers; Methods of erecting such structures
- E04H12/16—Prestressed structures
Definitions
- the present invention relates to a post-tensioned pole system.
- the present invention relates to a post-tensioned pole system includes one or more precast segments which are coupled to one another by a connector and post-tensioned through the use of at least one strand that is external to the wall thickness of the pole segments.
- poles are used in a wide variety of applications including electrical transmission and distribution environments, lighting, telecommunications and as supports for wind energy turbines. When used in these environments, the poles are subjected to forces from the wind, water and structural loads such as the weight of wire transmission lines or a wind turbine. These forces create a moment or torque that the pole must resist in order to remain in an upright position. In resisting these forces, the pole has a tendency to flex thereby putting the bottom portion of the pole in compression and the top portion of the pole in tension.
- the poles have been formed of various materials such as steel, wood, concrete, masonry materials and any combination thereof.
- the use of concrete to form the poles is relatively common due to its availability.
- the use of concrete to form the poles suffers from a number of drawbacks. For instance, while concrete is capable of withstanding a substantial amount of compression force, its ability to resist tension is considerably low. Therefore, different techniques have been established in an effort to enhance the concretes ability to withstand the tension forces imposed on the pole.
- Pre-tensioning the concrete has been accomplished by embedding strands within the concrete walls of the concrete using a spun or static cast technique.
- the strands are arranged within the form prior to pouring the concrete. Both ends of each strand are jacked to place the strands in tension.
- the concrete is then placed into the form embedding the strands therein.
- the strands are cut after the concrete has gained adequate strength, releasing the force to the concrete.
- the tension in the strands places the concrete pole into compression thereby allowing it to withstand a greater amount of tension force.
- the spun cast technique is similar to the static method in that the strands are placed in the form prior to the addition of the concrete. However, instead of placing the concrete into a static form, the concrete is poured into a machine that spins the concrete forcing the concrete to the outer walls of the form and embedding the strands within the wall of the structure.
- the aforementioned pre-tensioning techniques also suffer from a number of deficiencies.
- One problem with the spun cast method is that the concrete aggregate separates due to centrifugal force thereby making concrete weak and susceptible to cracking due to unequal distribution of aggregate.
- the equipment used to spin the concrete is expensive.
- both of the aforementioned methods of pre-tensioning concrete poles are problematic in that it takes a considerable amount of time to properly position the strands in the form prior to pouring the concrete.
- the concrete structures that are used in these environments are typically unitary structures that extend to a height of about 80-90 feet. This is problematic because certain power transmission line applications may require the poles to extend to greater heights. Additionally, given the fact that poles are a unitary structure, it is very difficult to transport the pole structures from an off-site location to the construction site. Once the poles arrive at the site, they require large cranes and heavy machinery to lift them into position due to the weight and length of the pole.
- a precast post-tensioned segmental pole system that is capable of supporting a load and withstanding other external forces.
- the pole system includes several pole segments with similar connectors anchoring them together.
- the first and second pole segments each have top and bottom ends with a cavity formed therein.
- the connector is adapted to couple the top end of the first pole segment with the bottom end of the second pole segment.
- the connector includes upper and lower pieces.
- the upper piece includes a channel band coupled to the second pole segment and having an inner edge.
- the connector further includes a stiffener being disposed within the channel band.
- the lower piece includes a base plate coupled to the first pole segment and a cover plate coupled to the base plate and having an outer edge that is adapted to interlock with an inner edge of the upper piece.
- the strands are placed in tension and can either continue through or be anchored at any of the segment connectors.
- the pole system may also include an anchor that couples the anchored strand to the connector.
- the anchor may include a cylinder, a clasping mechanism slidably received within the cylinder, a pipe coupled to the cylinder and a spring mounted within the pipe. The spring retains the clasping mechanism within the cylinder when the strand is coupled when the clasping mechanism is releasably coupled to the anchored strand.
- FIG. 1 is an elevational view of a post-tensioned segmental pole system according to the present invention
- FIG. 2 is a cross-sectional view taken along line 2 - 2 of FIG. 1 showing a connector mounted to a pole segment;
- FIG. 3 is a cross-sectional view taken along line 3 - 3 of FIG. 2 showing a plurality of strands extending within the cavity of the pole segment;
- FIG. 4 is an enlarged view of the area encompassed by “4” in FIG. 3 showing the connector mounted between two pole segments;
- FIG. 5 is an enlarged view of the area encompassed by “5” in FIG. 4 showing an anchor coupled to a strand;
- FIG. 6 is a perspective view showing an upper piece of the connector mounted to a pole segment
- FIG. 7 is a perspective view of an external form used to form the external shape of a pole segment
- FIG. 8 is an elevational view of the external mold with an internal mold positioned therein;
- FIG. 9 is an elevational view of the external mold showing a top piece rotating about a hinge point as illustrated in dashed lines;
- FIG. 10 is an elevational view of the internal mold having a tapered top piece
- FIG. 11 is an elevational view of an internal mold similar to FIG. 10 having a non-tapered top piece.
- pole system 10 generally designates a post-tensioned segmental pole system constructed in accordance with a first preferred embodiment of the present invention.
- Pole system 10 may include one or more pole segments 12 coupled to one another by a connector 14 to form a monopole structure.
- pole system 10 also includes a plurality of strands or tendons 16 that extend through a hollow interior cavity 18 , and which are external to pole segment 12 . Strands 16 are placed under tension and coupled between pole segments 12 .
- Pole system 10 may be used to support a load such as a structural appurtenance, insulator anchor, antenna in various types of service environments including, but not limited, to electrical transmission and distribution, lighting, communications and wind power generation.
- pole system 10 may also withstand external forces such as, but not limited to, wind, water and the like.
- a number of pole systems may be used in conjunction to form a multi-pole system to increase the height capability of pole system 10 .
- a number of pole systems may be arranged in a tripod configuration to provide support for a single pole system that would extend upwardly from the apex of the tripod. This configuration would essentially double the overall height capabilities of the present invention.
- pole system 10 may include one to four pole segments 12 that may form a monopole structure of up to 120 feet (36 meters). With additional reference to FIGS. 2 and 3 , each pole segment 12 may be approximately 30 feet (9 meters) in length having a tapered hexagonal cross-section. It is desirable to use a pole segment 12 having a cross-section that has stiffness characteristics that are independent of lateral applied loads such as, but not limited to, wind or wave forces. Therefore, it is preferable to use a pole segment 12 having a radial symmetrical cross-section with a flat outer surface 20 so that appurtenances may be fastened to pole segment 12 . Although a hexagonal cross-section is described and shown herein, it is within the scope of the present invention to use a pole segment 12 having cross-section in the shape of an octagon or any other radially symmetric cross-sectional shape.
- outer surface 20 of pole segment may be tapered at the rate of 1 inch (25 mm) over a distance of 10 feet as pole segment 12 extends from a bottom portion 22 to a top portion 24 .
- an inner surface 26 of pole segment 12 also tapers inwardly at approximately the same rate as outer surface 20 and defines hollow interior cavity 18 .
- Top portion 24 of inner surface 26 may include a thickened portion 28 where inner surface 26 tapers inwardly at a greater rate compared to bottom portion 22 of inner surface 26 . Thickened portion 28 may begin at an intermediate portion of inner surface 26 and extend to a rim 30 at top portion 24 .
- a plurality of apertures 32 are formed in inner surface 26 and extend through thickened portion 28 to a top surface 34 of pole segment 12 .
- Apertures 32 are hexagonally disposed within hollow interior cavity 18 and adapted to allow strands 16 to pass therethrough.
- the number of apertures 32 formed in segment 12 preferably corresponds with the number of strands 16 extending within cavity 18 .
- Pole segments 12 may be formed of various types of concrete including, but not limited to, high performance concrete (HPC) which is capable of higher than normal compressive strengths.
- High performance concrete utilizes fibers that are used to reinforce the concrete instead of using standard reinforced bars to enhance the concrete strength.
- the high performance concrete may have a minimum compressive strength of 8000 pounds per square inch, a RCP factor of 1000 coulombs, and a minimum freeze-thaw capacity for cold weather environments.
- pole system 10 may also utilize reinforcement bars or welded wire fabric within the walls of pole segments 12 to increase the strength of pole segment 12 .
- connector 14 is used to couple two pole segments 12 to one another.
- connector 14 includes an upper piece 36 and a lower piece 38 .
- Upper piece 36 includes a channel band 40 and a plurality of studs 42 . Studs 42 are mounted within bottom portion 22 of pole segment 12 .
- channel band 40 includes top and bottom plates 44 , 46 , a cross piece 48 and a stiffener 50 .
- Top plate 44 is fixedly coupled to studs 42 and extends inwardly towards cavity 18 .
- Cross piece 48 extends downwardly from top plate 44 and is coupled to bottom plate 46 .
- Bottom plate 46 extends inwardly and parallel with top plate 44 .
- bottom plate has a inner edge 52 that is adapted to interlock with lower piece 38 .
- inner edge 52 is in the shape of a hexagon, it should be understood that it may be formed in any shape that will allow it to interlock with lower piece 38 .
- Stiffeners 50 extend between top and bottom plates 44 , 46 and are used to stiffen channel band 40 .
- lower piece 38 is mounted to top portion 24 of pole segment 12 and is used to interlock with upper piece 36 .
- Lower piece 38 includes a cover plate 54 , a base plate 56 and studs 58 . Studs 58 are mounted within top portion 24 of pole segment and is fixedly mounted to base plate 56 .
- Base plate 56 is a hexagonal ring and has a support surface 60 .
- Cover plate 54 is also a hexagonal ring and mounted to a portion of a support surface 60 on base plate 56 . Further, cover plate 54 includes an outer edge 62 adapted to interlock with inner edge 52 of channel band 40 .
- outer edge 62 is shaped in the form of a hexagon, it should be understood and appreciated that outer edge 62 may be other shapes that will allow it to interlock with inner edge 52 of channel band 40 .
- Outer edge 62 is sized so that there is a gap 64 between inner edge 52 and outer edge 62 . However, gap 64 is small enough that the rotation between channel band 40 and cover plate 54 is minimized.
- Cover plate 54 also includes a rim 66 that may be aligned with rim 30 formed in top portion 24 of pole segment 12 . Further, as best seen in FIG. 5 , cover plate 54 has a plurality of holes 68 formed therein that are aligned with apertures 32 formed in thickened portion 28 so that strands 16 may pass therethrough. With reference to FIGS. 2 and 5 , cover plate 54 also has a top surface 70 where one or more strand anchors 72 may be mounted thereon which will be described more fully below.
- the post-tensioning of pole system 10 is accomplished through the use of a plurality of strands 16 that extend within hollow interior cavity 18 , but which are external to the walls of pole segments 12 .
- Strands 16 are adapted to be placed in tension so that pole segments 12 in pole system 10 are capable of withstanding an increased amount of tensile force.
- Strands 16 may be 0.5 inches (12 mm) in diameter and arranged within cavity 18 as shown in FIGS. 2 and 3 .
- strands 16 may be arranged in repeats on each of the side of the hexagonal cross-section of pole segment 12 so the resulting radial symmetry provides relatively constant moments of inertia for flexural stiffness independent of lateral force direction.
- strands 16 may extend through thickened portion 28 to ensure that strands 16 are positioned near inner surface 26 to allow them to make a maximum contribution to flexural stiffness.
- One strand 16 may extend from bottom portion 22 and be coupled to top end 22 , 24 of the same pole segment 12 .
- strand 16 may also extend from bottom portion 22 of a base pole segment 12 to a top portion 24 of a pole segment positioned on top of the base pole segment. Further, strands 16 may continue to extend to a pole segment further up the pole system 10 .
- Anchors 72 are coupled to top portion 24 of pole segment 12 through the use of at least one anchor 72 .
- anchor 72 rests against top surface 70 of cover plate 54 and prevents strand 16 from being pulled downwardly towards bottom portion 22 of pole segment 12 .
- Anchors 72 include a cylinder 74 having a clamping mechanism 76 slidably coupled within an interior portion of cylinder 74 .
- Clamping mechanism 76 is a two-piece jaw structure having a variable diameter hole formed therein. The hole is tapered as it extends through the jaws and has one or more teeth or protrusions extending therein to grip and hold onto strand 16 .
- Anchor 72 further includes a pipe 78 with a helical spring 80 fixedly mounted therein. Pipe 78 is fixedly mounted to the top ring of cylinder 74 and spring 80 is positioned to bias jaws 76 toward top surface 70 of cover plate 54 .
- pole system 10 may be a single pole segment 12 used alone, or in combination with one or more pole segments.
- a single or monopole system may extend to a height of 30 feet. Therefore, a system with four pole segments may extends to a height of 120 feet. Furthermore, a tripod system may extend to a height of approximately 240 feet. If one pole segment 12 is used by itself as the supporting structure, strands 16 are fed through hollow interior cavity 18 of pole segment and threaded through apertures 32 and holes 68 in cover plate 54 as best seen in FIGS. 3 and 4 . Referring now to FIG. 5 , a portion of each strand 16 that extends through holes 68 is coupled to anchor 72 .
- strand 16 is pushed upwardly against jaws 76 to place the end portion of strand 16 within the hole formed between jaws 76 .
- jaws 76 slide upwardly to compress spring 80 .
- Spring 80 prevents the jaws 76 from being dislodged from cylinder 74 .
- the angled portion of the jaws slides along an inner edge of cylinder 74 and the jaws splits apart.
- Strands 16 then proceed to extend downwardly to bottom portion 22 of pole segment 12 .
- Bottom portion 22 of pole segment 12 is placed in a foundation hole and backfill such as compact fill, flowable concrete mix or reinforced concrete is added to the hole to support pole segment 12 .
- Strands 16 are placed in tension by jacking or by other conventional methods to complete the post-tensioned pole system 10 .
- Two or more pole segments 12 may also be used to form pole system 10 .
- Strands 16 are first fed through hollow interior cavity 18 of the bottom or base pole segment and external to the pole segment structure 12 .
- Strands 16 are threaded through apertures 32 and holes 68 in cover plate 54 .
- Some of strands 16 are then coupled to top surface 70 of cover plate 54 by anchors 72 as described in detail above.
- the remaining strands continue to extend through the hollow interior cavity 18 of the second pole segment.
- Bottom plate 48 is placed on support surface 60 and inner edge 52 is interlocked with outer edge 62 as best seen in FIGS. 2 and 4 .
- the second pole segment is resting on top of the bottom or base pole segment.
- the remaining strands 16 are threaded through apertures 32 and holes 68 in cover plate 54 of the second pole segment.
- All the remaining strands 16 may be coupled to cover plate 54 of the second pole segment by using strand anchors 72 , or in the alternative, some strands 16 may be coupled to cover plate 54 while the remaining strands 16 continue to extend to a third pole segment. This process may continue in a similar fashion as described above until the desired height is achieved. For example, in a four pole system as shown in FIG. 1 , thirty-six strands may extend within the cavity 18 of a bottom or base pole segment. At the juncture between the base segment and second segment, twelve of those strands may be mounted to cover plate on the base segment and twenty-four would continue to extend within cavity of the second pole segment. The juncture between the second and third pole segments is best shown in FIGS. 2 and 3 .
- pole segments 12 and strands 16 may be conducted on the ground so the pole segments extend in a horizontal direction, or may be stacked on top of each other for vertical construction.
- strands 16 in the multi-segmented construction are then placed in tension to create a post-tensioned pole system 10 and placed in the appropriate foundation as described above.
- concrete may then be poured through rims 30 , 66 into hollow interior portion 18 in either the single or multi-pole segment structures to create a solid pole structure.
- the present invention further includes a mold unit 82 that may be used to precast pole segments 12 that are used in pole system 10 as best seen in FIG. 8 .
- Mold unit 82 includes an external mold 84 , internal mold 86 and a yoke 88 .
- Mold unit 82 shown in the accompanying drawings is an example of a typical mold structure, and it will be understood that the proportions of the molds may vary depending on where the pole segment will be located in the pole system 10 . For instance, a pole segment that will be positioned at the base or bottom of pole system will be much larger than a mold for a segment that will be positioned at the upper portions of pole system 10 .
- external mold 84 includes a bottom piece 90 and a pair of top pieces 92 .
- top pieces 92 are coupled to bottom piece 90 by a set of hinges 94 which allow external mold 84 to be placed in closed and open positions.
- external mold 84 is in a closed position where bottom piece 90 and top pieces 92 are arranged to form a channel 96 which will define the outer surface 20 of pole segment 12 .
- channel 96 may also taper inwardly along the longitudinal axis of external mold 84 . As best seen in FIG.
- top pieces 92 may be rotated outwardly about hinges 94 so that external mold 84 is in the open position so that pole segment 12 may be removed from external mold 84 .
- external mold 84 also has a plurality of bolts 98 adjustably mounted within bottom piece 90 .
- Bolts 98 are mounted within bottom piece 90 so that a portion of each bolt 98 can be independently adjusted to extend variable distances within channel 96 and contact internal mold 86 . It is also within the scope of this invention to include bolts 98 in top pieces 92 .
- Yoke 88 is removably coupled to a top surface 98 top pieces 92 and has a bolt 100 mounted thereto that is adapted to extend within channel 96 and contact internal mold 86 .
- Yoke 88 is used to prevent top pieces 92 from floating or rotating relative to bottom piece 90 when the concrete is placed within mold unit 82 .
- internal mold 86 is tubular member having a top piece 102 , a bottom piece 104 and a plurality of tubes 106 .
- bottom piece has an outer surface 108 that has a similar taper compared to channel 96 , but is sized so there is a space between channel 96 and outer surface 108 .
- a collar 110 removably couples bottom piece 104 to top piece 102 .
- An outer surface 112 of top piece 102 extends upwardly from collar 110 at the same taper as bottom piece 104 and then proceeds to narrow even further as it extends toward a rim 114 .
- Tubes 106 are used to form apertures 32 in thickened portion 28 of pole segment 12 .
- tubes 106 are mounted to top piece 102 and extend outwardly therefrom in a direction parallel to the longitudinal axis of top and bottom pieces 102 , 104 .
- the distal ends of tubes 106 are tapered to make it easier to remove tubes with top and bottom pieces 102 , 104 after the concrete hardens.
- top piece 102 may also have a uniform taper that is similar to bottom piece 104 as it extends from collar 110 to rim 114 .
- collar 110 is loosened, and the new top piece is slid onto bottom piece 104 .
- Collar 110 is tightened and the change is complete.
- the uniform taper in top piece 102 results in a pole segment 12 with uniform wall thickness along its entire length. In this case, there would be no thickened portion 28 or apertures formed in pole segment 12 since strands 16 may pass through hollow interior cavity 18 without interfering with the walls of pole segment 12 .
- top pieces 92 on external mold 84 are rotated outwardly about hinges 94 to an open position.
- internal mold 86 is then placed within channel 96 and supported by bolts 100 .
- Bolts 100 are adjusted in such a manner so that there is an equal amount of space between channel 96 and outer surfaces 108 , 112 of internal mold 86 .
- Top pieces 92 are then moved to the closed position.
- Yoke 88 is then placed on top surface 98 and is coupled to each top piece 92 to prevent top pieces 92 from rotating outwardly relative to bottom piece 90 . Concrete is then poured between channel 96 and outer surfaces 108 , 112 .
- pole segment 12 may them be removed from external mold 84 and used in pole system 10 . It should be understood that pole segments may be formed either at an off-site location or a construction site.
- the invention is one that is designed to overcome the drawbacks and deficiencies existing in the prior art.
- the invention provides a pole system that includes one or more pole segments that are post-tensioned by strands that are positioned within a hollow interior cavity and external to the wall structure of the pole segments.
- the use of separate pole segments to form the pole system reduces the difficulty in transporting the components of the pole system.
- Each pole segment is relatively easy to maneuver and lift through the use of a crane, winch system, or helicopter to simplify installation.
- the fact that the strands are positioned within the hollow interior cavity of the pole segment reduces the amount of time it takes to manufacture the pole segments since each strand does not have to be positioned within the form prior to pouring the concrete in the form.
- the connectors provided in the present invention simplify the process of coupling two pole segments to one another.
- the forms of the present invention eliminates the need to purchase expensive spinning equipment for forming pole segments having a interior cavity.
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Abstract
A precast post-tensioned segmental pole system capable of supporting a load is provided. The pole system includes a plurality of pole segments that use connectors and strands to anchor them together. The strands extend within a cavity formed in the pole segments and are external to the wall structure of the pole segments. The strands may be coupled between both of the pole segments, or be anchored to a connector. The connector includes an upper piece that is coupled to one pole segment, and a lower piece that is coupled to the other pole segment. Upper and lower pieces interlock with each other to join the pole segments to one another. The strands are placed in tension so that pole system is capable of withstanding forces imposed by the load.
Description
- This application claims the benefit of U.S. patent application Ser. No. 10/184,349, filed Jun. 27, 2002, which claims benefit of U.S. Provisional Application No. 60/301,189, filed Jun. 27, 2001.
- Not Applicable.
- The present invention relates to a post-tensioned pole system. In particular, the present invention relates to a post-tensioned pole system includes one or more precast segments which are coupled to one another by a connector and post-tensioned through the use of at least one strand that is external to the wall thickness of the pole segments.
- It is well known that poles are used in a wide variety of applications including electrical transmission and distribution environments, lighting, telecommunications and as supports for wind energy turbines. When used in these environments, the poles are subjected to forces from the wind, water and structural loads such as the weight of wire transmission lines or a wind turbine. These forces create a moment or torque that the pole must resist in order to remain in an upright position. In resisting these forces, the pole has a tendency to flex thereby putting the bottom portion of the pole in compression and the top portion of the pole in tension.
- In the past, the poles have been formed of various materials such as steel, wood, concrete, masonry materials and any combination thereof. The use of concrete to form the poles is relatively common due to its availability. However, the use of concrete to form the poles suffers from a number of drawbacks. For instance, while concrete is capable of withstanding a substantial amount of compression force, its ability to resist tension is considerably low. Therefore, different techniques have been established in an effort to enhance the concretes ability to withstand the tension forces imposed on the pole.
- One technique used to enhance the ability of the concrete to withstand tension forces is pre-tensioning. Pre-tensioning the concrete has been accomplished by embedding strands within the concrete walls of the concrete using a spun or static cast technique. In the static cast method, the strands are arranged within the form prior to pouring the concrete. Both ends of each strand are jacked to place the strands in tension. The concrete is then placed into the form embedding the strands therein. The strands are cut after the concrete has gained adequate strength, releasing the force to the concrete. The tension in the strands places the concrete pole into compression thereby allowing it to withstand a greater amount of tension force. The spun cast technique is similar to the static method in that the strands are placed in the form prior to the addition of the concrete. However, instead of placing the concrete into a static form, the concrete is poured into a machine that spins the concrete forcing the concrete to the outer walls of the form and embedding the strands within the wall of the structure.
- The aforementioned pre-tensioning techniques also suffer from a number of deficiencies. One problem with the spun cast method is that the concrete aggregate separates due to centrifugal force thereby making concrete weak and susceptible to cracking due to unequal distribution of aggregate. In addition, the equipment used to spin the concrete is expensive. In addition, both of the aforementioned methods of pre-tensioning concrete poles are problematic in that it takes a considerable amount of time to properly position the strands in the form prior to pouring the concrete.
- Additionally, there other problems associated with current concrete pole structures. For example, the concrete structures that are used in these environments are typically unitary structures that extend to a height of about 80-90 feet. This is problematic because certain power transmission line applications may require the poles to extend to greater heights. Additionally, given the fact that poles are a unitary structure, it is very difficult to transport the pole structures from an off-site location to the construction site. Once the poles arrive at the site, they require large cranes and heavy machinery to lift them into position due to the weight and length of the pole.
- Accordingly, there remains a need for a segmental post-tensioned pole system that increases maximum height of pole while reducing the difficulty in transporting the pole from off-site location to the construction site. In addition, there is also a need to simplify the installation and manufacture of the pole. The present invention fills these needs as well as various other needs.
- In order to overcome the above-stated problems and limitations, and to achieve the noted objects, there is provided a precast post-tensioned segmental pole system that is capable of supporting a load and withstanding other external forces.
- In general, the pole system includes several pole segments with similar connectors anchoring them together. For example, the first and second pole segments each have top and bottom ends with a cavity formed therein. The connector is adapted to couple the top end of the first pole segment with the bottom end of the second pole segment. The connector includes upper and lower pieces. The upper piece includes a channel band coupled to the second pole segment and having an inner edge. The connector further includes a stiffener being disposed within the channel band. The lower piece includes a base plate coupled to the first pole segment and a cover plate coupled to the base plate and having an outer edge that is adapted to interlock with an inner edge of the upper piece. The strands are placed in tension and can either continue through or be anchored at any of the segment connectors.
- Additionally, the pole system may also include an anchor that couples the anchored strand to the connector. The anchor may include a cylinder, a clasping mechanism slidably received within the cylinder, a pipe coupled to the cylinder and a spring mounted within the pipe. The spring retains the clasping mechanism within the cylinder when the strand is coupled when the clasping mechanism is releasably coupled to the anchored strand.
- Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached figures.
- In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are employed to indicate like parts in the various views:
-
FIG. 1 is an elevational view of a post-tensioned segmental pole system according to the present invention; -
FIG. 2 is a cross-sectional view taken along line 2-2 ofFIG. 1 showing a connector mounted to a pole segment; -
FIG. 3 is a cross-sectional view taken along line 3-3 ofFIG. 2 showing a plurality of strands extending within the cavity of the pole segment; -
FIG. 4 is an enlarged view of the area encompassed by “4” inFIG. 3 showing the connector mounted between two pole segments; -
FIG. 5 is an enlarged view of the area encompassed by “5” inFIG. 4 showing an anchor coupled to a strand; -
FIG. 6 is a perspective view showing an upper piece of the connector mounted to a pole segment; -
FIG. 7 is a perspective view of an external form used to form the external shape of a pole segment; -
FIG. 8 is an elevational view of the external mold with an internal mold positioned therein; -
FIG. 9 is an elevational view of the external mold showing a top piece rotating about a hinge point as illustrated in dashed lines; -
FIG. 10 is an elevational view of the internal mold having a tapered top piece; and -
FIG. 11 is an elevational view of an internal mold similar toFIG. 10 having a non-tapered top piece. - Referring now to the drawings in detail, and initially to
FIG. 1 , numeral 10 generally designates a post-tensioned segmental pole system constructed in accordance with a first preferred embodiment of the present invention.Pole system 10 may include one ormore pole segments 12 coupled to one another by aconnector 14 to form a monopole structure. As best seen inFIG. 3 ,pole system 10 also includes a plurality of strands ortendons 16 that extend through a hollowinterior cavity 18, and which are external topole segment 12.Strands 16 are placed under tension and coupled betweenpole segments 12. -
Pole system 10 may be used to support a load such as a structural appurtenance, insulator anchor, antenna in various types of service environments including, but not limited, to electrical transmission and distribution, lighting, communications and wind power generation. In addition,pole system 10 may also withstand external forces such as, but not limited to, wind, water and the like. It will be understood that a number of pole systems may be used in conjunction to form a multi-pole system to increase the height capability ofpole system 10. For instance, a number of pole systems may be arranged in a tripod configuration to provide support for a single pole system that would extend upwardly from the apex of the tripod. This configuration would essentially double the overall height capabilities of the present invention. - As best seen in
FIG. 1 ,pole system 10 may include one to fourpole segments 12 that may form a monopole structure of up to 120 feet (36 meters). With additional reference toFIGS. 2 and 3 , eachpole segment 12 may be approximately 30 feet (9 meters) in length having a tapered hexagonal cross-section. It is desirable to use apole segment 12 having a cross-section that has stiffness characteristics that are independent of lateral applied loads such as, but not limited to, wind or wave forces. Therefore, it is preferable to use apole segment 12 having a radial symmetrical cross-section with a flatouter surface 20 so that appurtenances may be fastened topole segment 12. Although a hexagonal cross-section is described and shown herein, it is within the scope of the present invention to use apole segment 12 having cross-section in the shape of an octagon or any other radially symmetric cross-sectional shape. - As best seen in
FIG. 1 ,outer surface 20 of pole segment may be tapered at the rate of 1 inch (25 mm) over a distance of 10 feet aspole segment 12 extends from abottom portion 22 to atop portion 24. As best seen inFIGS. 3 and 4 , aninner surface 26 ofpole segment 12 also tapers inwardly at approximately the same rate asouter surface 20 and defines hollowinterior cavity 18.Top portion 24 ofinner surface 26 may include a thickenedportion 28 whereinner surface 26 tapers inwardly at a greater rate compared tobottom portion 22 ofinner surface 26.Thickened portion 28 may begin at an intermediate portion ofinner surface 26 and extend to arim 30 attop portion 24. Further, a plurality ofapertures 32 are formed ininner surface 26 and extend through thickenedportion 28 to atop surface 34 ofpole segment 12.Apertures 32 are hexagonally disposed within hollowinterior cavity 18 and adapted to allowstrands 16 to pass therethrough. The number ofapertures 32 formed insegment 12 preferably corresponds with the number ofstrands 16 extending withincavity 18. -
Pole segments 12 may be formed of various types of concrete including, but not limited to, high performance concrete (HPC) which is capable of higher than normal compressive strengths. High performance concrete utilizes fibers that are used to reinforce the concrete instead of using standard reinforced bars to enhance the concrete strength. The high performance concrete may have a minimum compressive strength of 8000 pounds per square inch, a RCP factor of 1000 coulombs, and a minimum freeze-thaw capacity for cold weather environments. However,pole system 10 may also utilize reinforcement bars or welded wire fabric within the walls ofpole segments 12 to increase the strength ofpole segment 12. - As best seen in
FIG. 1 ,connector 14 is used to couple twopole segments 12 to one another. As best seen inFIG. 4 ,connector 14 includes anupper piece 36 and alower piece 38.Upper piece 36 includes achannel band 40 and a plurality ofstuds 42.Studs 42 are mounted withinbottom portion 22 ofpole segment 12. With additional reference toFIG. 6 ,channel band 40 includes top andbottom plates cross piece 48 and astiffener 50.Top plate 44 is fixedly coupled tostuds 42 and extends inwardly towardscavity 18.Cross piece 48 extends downwardly fromtop plate 44 and is coupled tobottom plate 46.Bottom plate 46 extends inwardly and parallel withtop plate 44. As best seen inFIGS. 2 and 6 , bottom plate has ainner edge 52 that is adapted to interlock withlower piece 38. Although,inner edge 52 is in the shape of a hexagon, it should be understood that it may be formed in any shape that will allow it to interlock withlower piece 38.Stiffeners 50 extend between top andbottom plates channel band 40. - As best seen in
FIGS. 2 and 4 ,lower piece 38 is mounted totop portion 24 ofpole segment 12 and is used to interlock withupper piece 36.Lower piece 38 includes acover plate 54, abase plate 56 andstuds 58.Studs 58 are mounted withintop portion 24 of pole segment and is fixedly mounted tobase plate 56.Base plate 56 is a hexagonal ring and has asupport surface 60.Cover plate 54 is also a hexagonal ring and mounted to a portion of asupport surface 60 onbase plate 56. Further,cover plate 54 includes anouter edge 62 adapted to interlock withinner edge 52 ofchannel band 40. Althoughouter edge 62 is shaped in the form of a hexagon, it should be understood and appreciated thatouter edge 62 may be other shapes that will allow it to interlock withinner edge 52 ofchannel band 40.Outer edge 62 is sized so that there is agap 64 betweeninner edge 52 andouter edge 62. However,gap 64 is small enough that the rotation betweenchannel band 40 andcover plate 54 is minimized.Cover plate 54 also includes arim 66 that may be aligned withrim 30 formed intop portion 24 ofpole segment 12. Further, as best seen inFIG. 5 ,cover plate 54 has a plurality ofholes 68 formed therein that are aligned withapertures 32 formed in thickenedportion 28 so thatstrands 16 may pass therethrough. With reference toFIGS. 2 and 5 ,cover plate 54 also has atop surface 70 where one or more strand anchors 72 may be mounted thereon which will be described more fully below. - The post-tensioning of
pole system 10 is accomplished through the use of a plurality ofstrands 16 that extend within hollowinterior cavity 18, but which are external to the walls ofpole segments 12.Strands 16 are adapted to be placed in tension so thatpole segments 12 inpole system 10 are capable of withstanding an increased amount of tensile force.Strands 16 may be 0.5 inches (12 mm) in diameter and arranged withincavity 18 as shown in FIGS. 2 and 3. In particular,strands 16 may be arranged in repeats on each of the side of the hexagonal cross-section ofpole segment 12 so the resulting radial symmetry provides relatively constant moments of inertia for flexural stiffness independent of lateral force direction. With specific reference toFIG. 4 ,strands 16 may extend through thickenedportion 28 to ensure thatstrands 16 are positioned nearinner surface 26 to allow them to make a maximum contribution to flexural stiffness. Onestrand 16 may extend frombottom portion 22 and be coupled totop end same pole segment 12. In addition,strand 16 may also extend frombottom portion 22 of abase pole segment 12 to atop portion 24 of a pole segment positioned on top of the base pole segment. Further,strands 16 may continue to extend to a pole segment further up thepole system 10. - As best seen in
FIGS. 2 and 5 ,strands 16 are coupled totop portion 24 ofpole segment 12 through the use of at least oneanchor 72. Specifically,anchor 72 rests againsttop surface 70 ofcover plate 54 and preventsstrand 16 from being pulled downwardly towardsbottom portion 22 ofpole segment 12.Anchors 72 include acylinder 74 having aclamping mechanism 76 slidably coupled within an interior portion ofcylinder 74. Clampingmechanism 76 is a two-piece jaw structure having a variable diameter hole formed therein. The hole is tapered as it extends through the jaws and has one or more teeth or protrusions extending therein to grip and hold ontostrand 16.Anchor 72 further includes apipe 78 with ahelical spring 80 fixedly mounted therein.Pipe 78 is fixedly mounted to the top ring ofcylinder 74 andspring 80 is positioned to biasjaws 76 towardtop surface 70 ofcover plate 54. - In operation,
pole system 10 may be asingle pole segment 12 used alone, or in combination with one or more pole segments. A single or monopole system may extend to a height of 30 feet. Therefore, a system with four pole segments may extends to a height of 120 feet. Furthermore, a tripod system may extend to a height of approximately 240 feet. If onepole segment 12 is used by itself as the supporting structure,strands 16 are fed through hollowinterior cavity 18 of pole segment and threaded throughapertures 32 and holes 68 incover plate 54 as best seen inFIGS. 3 and 4 . Referring now toFIG. 5 , a portion of eachstrand 16 that extends throughholes 68 is coupled toanchor 72. In particular,strand 16 is pushed upwardly againstjaws 76 to place the end portion ofstrand 16 within the hole formed betweenjaws 76. Asstrand 16 is being pushed upwardly,jaws 76 slide upwardly to compressspring 80.Spring 80 prevents thejaws 76 from being dislodged fromcylinder 74. The angled portion of the jaws slides along an inner edge ofcylinder 74 and the jaws splits apart. Oncejaws 76 open enough to allowstrand 16 to enter the inner diameter, the upward force on strands is release andspring 80biased jaws 76 downwardly so that the hold formed between the jaws decreases and the teeth within the hole grips ontostrand 16. The remainingstrands 16 are coupled totop portion 24 of pole segment in a similar fashion.Strands 16 then proceed to extend downwardly tobottom portion 22 ofpole segment 12.Bottom portion 22 ofpole segment 12 is placed in a foundation hole and backfill such as compact fill, flowable concrete mix or reinforced concrete is added to the hole to supportpole segment 12.Strands 16 are placed in tension by jacking or by other conventional methods to complete thepost-tensioned pole system 10. - Two or
more pole segments 12 may also be used to formpole system 10.Strands 16 are first fed through hollowinterior cavity 18 of the bottom or base pole segment and external to thepole segment structure 12.Strands 16 are threaded throughapertures 32 and holes 68 incover plate 54. Some ofstrands 16 are then coupled totop surface 70 ofcover plate 54 byanchors 72 as described in detail above. The remaining strands continue to extend through the hollowinterior cavity 18 of the second pole segment.Bottom plate 48 is placed onsupport surface 60 andinner edge 52 is interlocked withouter edge 62 as best seen inFIGS. 2 and 4 . Thus, the second pole segment is resting on top of the bottom or base pole segment. The remainingstrands 16 are threaded throughapertures 32 and holes 68 incover plate 54 of the second pole segment. - All the remaining
strands 16 may be coupled to coverplate 54 of the second pole segment by using strand anchors 72, or in the alternative, somestrands 16 may be coupled to coverplate 54 while the remainingstrands 16 continue to extend to a third pole segment. This process may continue in a similar fashion as described above until the desired height is achieved. For example, in a four pole system as shown inFIG. 1 , thirty-six strands may extend within thecavity 18 of a bottom or base pole segment. At the juncture between the base segment and second segment, twelve of those strands may be mounted to cover plate on the base segment and twenty-four would continue to extend within cavity of the second pole segment. The juncture between the second and third pole segments is best shown inFIGS. 2 and 3 . At this juncture, twelve of those strands may be mounted to coverplate 54 of the second pole segment and twelve would continue to extend withincavity 18 of the third pole segment. At the juncture between the third and fourth pole segments, six of those strands may be mounted to cover plate of the third pole segment and six would continue to extend within cavity of the fourth pole segment. Finally, the six remaining strands would then be coupled to the cover plate of the fourth pole segment. It will be understood that the joining ofpole segments 12 andstrands 16 may be conducted on the ground so the pole segments extend in a horizontal direction, or may be stacked on top of each other for vertical construction. Regardless of the number of strands inpole system 10,strands 16 in the multi-segmented construction are then placed in tension to create apost-tensioned pole system 10 and placed in the appropriate foundation as described above. In addition, concrete may then be poured throughrims interior portion 18 in either the single or multi-pole segment structures to create a solid pole structure. - The present invention further includes a
mold unit 82 that may be used toprecast pole segments 12 that are used inpole system 10 as best seen inFIG. 8 .Mold unit 82 includes anexternal mold 84,internal mold 86 and ayoke 88.Mold unit 82 shown in the accompanying drawings is an example of a typical mold structure, and it will be understood that the proportions of the molds may vary depending on where the pole segment will be located in thepole system 10. For instance, a pole segment that will be positioned at the base or bottom of pole system will be much larger than a mold for a segment that will be positioned at the upper portions ofpole system 10. - As best seen in
FIG. 7 ,external mold 84 includes abottom piece 90 and a pair oftop pieces 92. In particular,top pieces 92 are coupled tobottom piece 90 by a set ofhinges 94 which allowexternal mold 84 to be placed in closed and open positions. As best seen inFIG. 7 ,external mold 84 is in a closed position wherebottom piece 90 andtop pieces 92 are arranged to form achannel 96 which will define theouter surface 20 ofpole segment 12. In addition,channel 96 may also taper inwardly along the longitudinal axis ofexternal mold 84. As best seen inFIG. 9 ,top pieces 92 may be rotated outwardly about hinges 94 so thatexternal mold 84 is in the open position so thatpole segment 12 may be removed fromexternal mold 84. As best seen inFIG. 8 ,external mold 84 also has a plurality ofbolts 98 adjustably mounted withinbottom piece 90.Bolts 98 are mounted withinbottom piece 90 so that a portion of eachbolt 98 can be independently adjusted to extend variable distances withinchannel 96 and contactinternal mold 86. It is also within the scope of this invention to includebolts 98 intop pieces 92.Yoke 88 is removably coupled to atop surface 98top pieces 92 and has abolt 100 mounted thereto that is adapted to extend withinchannel 96 and contactinternal mold 86.Yoke 88 is used to preventtop pieces 92 from floating or rotating relative tobottom piece 90 when the concrete is placed withinmold unit 82. - As best seen in
FIG. 10 ,internal mold 86 is tubular member having atop piece 102, abottom piece 104 and a plurality oftubes 106. With additional reference toFIG. 8 , bottom piece has anouter surface 108 that has a similar taper compared tochannel 96, but is sized so there is a space betweenchannel 96 andouter surface 108. Further, acollar 110 removably couplesbottom piece 104 totop piece 102. Anouter surface 112 oftop piece 102 extends upwardly fromcollar 110 at the same taper asbottom piece 104 and then proceeds to narrow even further as it extends toward arim 114. The increased taper towards the top portion oftop piece 102 creates a larger space betweenchannel 96 andouter surface 112 to allow for the formation of thickenedportion 28 as seen inFIG. 4 .Tubes 106 are used to formapertures 32 in thickenedportion 28 ofpole segment 12. In particular,tubes 106 are mounted totop piece 102 and extend outwardly therefrom in a direction parallel to the longitudinal axis of top andbottom pieces tubes 106 are tapered to make it easier to remove tubes with top andbottom pieces - As best seen in
FIG. 11 ,top piece 102 may also have a uniform taper that is similar tobottom piece 104 as it extends fromcollar 110 torim 114. To changetop pieces 102,collar 110 is loosened, and the new top piece is slid ontobottom piece 104.Collar 110 is tightened and the change is complete. The uniform taper intop piece 102 results in apole segment 12 with uniform wall thickness along its entire length. In this case, there would be no thickenedportion 28 or apertures formed inpole segment 12 sincestrands 16 may pass through hollowinterior cavity 18 without interfering with the walls ofpole segment 12. - In forming a pole segment using
mold unit 82,top pieces 92 onexternal mold 84 are rotated outwardly about hinges 94 to an open position. As best seen inFIG. 8 ,internal mold 86 is then placed withinchannel 96 and supported bybolts 100.Bolts 100 are adjusted in such a manner so that there is an equal amount of space betweenchannel 96 andouter surfaces internal mold 86.Top pieces 92 are then moved to the closed position.Yoke 88 is then placed ontop surface 98 and is coupled to eachtop piece 92 to preventtop pieces 92 from rotating outwardly relative tobottom piece 90. Concrete is then poured betweenchannel 96 andouter surfaces internal mold 86 is removed from thehardened pole segment 12 thereby forming hollowinterior cavity 18 andapertures 32.Yoke 88 is then removed fromtop pieces 92 andtop pieces 92 are moved to the open position.Pole segment 12 may them be removed fromexternal mold 84 and used inpole system 10. It should be understood that pole segments may be formed either at an off-site location or a construction site. - It can, therefore, be seen that the invention is one that is designed to overcome the drawbacks and deficiencies existing in the prior art. The invention provides a pole system that includes one or more pole segments that are post-tensioned by strands that are positioned within a hollow interior cavity and external to the wall structure of the pole segments. The use of separate pole segments to form the pole system reduces the difficulty in transporting the components of the pole system. Each pole segment is relatively easy to maneuver and lift through the use of a crane, winch system, or helicopter to simplify installation. In addition, the fact that the strands are positioned within the hollow interior cavity of the pole segment reduces the amount of time it takes to manufacture the pole segments since each strand does not have to be positioned within the form prior to pouring the concrete in the form. Further, the connectors provided in the present invention simplify the process of coupling two pole segments to one another. Additionally, the forms of the present invention eliminates the need to purchase expensive spinning equipment for forming pole segments having a interior cavity.
- While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. Reasonable variation and modification are possible within the scope of the foregoing disclosure of the invention without departing from the spirit of the invention.
Claims (20)
1. A device for precasting a pole segment comprising:
an external mold comprising a bottom piece and a plurality of top pieces, said top pieces being hingedly coupled with said bottom piece, said bottom piece and said top pieces having inner surfaces defining a channel;
a yoke coupled to said top pieces; and
an internal mold having an outer surface, said internal mold adapted to be placed within said channel to thereby define a cavity between said outer surface of said internal mold and said inner surfaces of said bottom piece and said top pieces, whereby said inner surfaces shape an exterior surface of a pole segment and said outer surface of said internal mold shapes an interior surface of said pole segment when a formable material is placed between said external mold and said internal mold.
2. The device of claim 1 , further comprising an adjustable holding mechanism that extends through said external mold and braces said internal mold to hold said internal mold in position within said channel.
3. The device of claim 3 , wherein the adjustable holding mechanism consists of at least one bolt.
4. The device of claim 1 , wherein said internal mold includes top and bottom pieces.
5. The device of claim 4 wherein said bottom piece is tapered along its length.
6. The device of claim 4 wherein said top piece is tapered along its length.
7. The device of claim 6 , wherein a top portion of said top piece is further tapered to form a thickened portion in the pole segment.
8. The device of claim 7 , further comprising at least one tube coupled to said tapered portion of said internal mold.
9. A method for forming a pole segment used in a post-tensioned pole system, said method comprising:
providing an external form;
providing an internal form;
placing said internal form within said external form;
securing said internal form within said external form to thereby define a cavity between said internal form and said external form; and
placing a formable material within said cavity to form the pole segment.
10. The method of claim 9 wherein the external form includes a plurality of top pieces and a bottom piece.
11. The method of claim 10 , wherein the top pieces are hingedly coupled to said bottom pieces to form a channel.
12. The method of claim 11 further comprising providing at least one adjustable holding mechanism coupled to the external form.
13. The method of claim 12 further comprising adjusting said holding mechanism to secure internal form within said channel.
14. The method of claim 9 , wherein said internal form is tapered to form a thickened portion of the pole segment.
15. The method of claim 9 wherein said external form is tapered along its length.
16. The method of claim 15 , further including:
providing at least one tube; and
coupling said tube to said tapered portion of said internal mold prior to placing concrete mixture between said external and internal forms to create an aperture in the thickness portion of the pole segment.
17. A method for forming a pole segment used in a post-tensioned pole system, said method comprising:
providing a external form having a plurality of top pieces and a bottom piece, said top pieces being hingedly coupled to said bottom piece having inner surfaces defining a channel;
providing at least one adjustable holding mechanism coupled to said external form;
providing an internal form with an outer surface;
placing said internal form within said channel to thereby define a cavity between said outer surfaces of said internal form and said inner surfaces of said bottom and top pieces;
adjusting said holding mechanism so that said internal form is secured within said channel; and
placing a concrete mixture within the cavity to form the pole segment.
18. The method of claim 17 , wherein said internal form is tapered to form a thickened portion of the pole segment.
19. The method of claim 18 , further including:
providing at least one tube; and
coupling said tube to said tapered portion of said internal mold prior to placing concrete mixture between said external and internal forms to create an aperture in the thickness portion of the pole segment.
20. The method of claim 19 wherein said external form is tapered along its length.
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US11/011,275 US20050120644A1 (en) | 2001-06-27 | 2004-12-13 | Precast post-tensioned segmental pole system |
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US10/184,349 US6851231B2 (en) | 2001-06-27 | 2002-06-27 | Precast post-tensioned segmental pole system |
US11/011,275 US20050120644A1 (en) | 2001-06-27 | 2004-12-13 | Precast post-tensioned segmental pole system |
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US10/184,349 Division US6851231B2 (en) | 2001-06-27 | 2002-06-27 | Precast post-tensioned segmental pole system |
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US11/011,275 Abandoned US20050120644A1 (en) | 2001-06-27 | 2004-12-13 | Precast post-tensioned segmental pole system |
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US20030000165A1 (en) | 2003-01-02 |
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